Combustion regulation



Sept. 22, 1942. c. MEAD COMBUSTION REGULATION Filed March 28, 1959 gwucm/bom RALPH 0. MEAD m4; aw gyi -x.

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Patented Sept. 22, 1942 COMBUSTION REGULATION Ralph C. Mead, Worcester, Mass, assignor to Riley Stoker Corporation, Worcester, Mass., a corporation of Massachusetts Application March 28, 1939, Serial No. 264,607

4 Claims.

This invention relates to combustion regulation, and more particularly to the regulation of the draft in furnaces having a hydraulic stoker which is started automatically in response to demand for heat.

When the stoker is shut down between successive periods of operation it is desirable that the furnace dampers be closed, or nearly closed, to prevent excessive air flow through the furnace by natural draft. However, when the stoker is started again the furnace outlet damper must be opened to prevent a substantial increase in the furnace pressure, as otherwise flame and smoke will issue into the room from all cracks and openings in the furnace walls. Furthermore, if the forced draft damper is closed during the shut down period, it must be opened when the stoker is started, but if it is opened too quickly a momentarily excessive furnace pressure may result.

It is accordingly one object of the invention to provide a simple, inexpensive and reliable apparatus to open the furnace dampers upon the starting of the stoker.

It is a further object of the invention to provide a hydraulic stoker of the start-and-stop type, in combination with a simple arrangement of apparatus to prevent any appreciable increase in the furnace pressure when the stoker is started.

It is a further object of the invention to provide a hydraulic stoker of the start-and-stop type, in combination with a simple arrangement of apparatus to open the furnace dampers when the stoker is started and to close the dampers when the stoker is stopped.

With these and other objects in View, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

Referring to the drawing illustrating one embodiment of the invention, and in which like reference numerals indicate like parts:

Fig. 1 is a diagrammatic elevation, partly in section, of a furnace fired by a start-and-stop hydraulic stoker;

Fig. 2 is an enlarged detail of a check valve; and

Fig. 3 is an enlarged detail of ,a second check valve.

The embodiment illustrated comprises walls forming a furnace combustion chamber ll fired by means of an underfeed stoker l2 having a retort I4 and tuyere blocks I5. The stoker is actuated by a hydraulic motor l6 of any suitill draft fan l9 driven by a motor 20.

able construction. Air is supplied to the space l8 beneath the retort [4 by means of a forced The motor illustrated is an electric motor directly connected to the fan, and it also serves to actuate a pump 22 through a belt drive 23. A suitable liquid, such as oil, is supplied to the pump 22 from a tank or reservoir 24 through a pipe 26. A pipe 2'! conducts oil under pressure from the pump to the hydraulic motor l5, and an exhaust pipe 28 leads from this motor to the tank 24.

The heat from the furnace II is utilized to generate steam in a boiler 30 mounted thereabove. The furnace gases flow in contact with the boiler heating surfaces and then escape through a gas outlet or uptake 3| to a suitable stack (not shown). The escape of these gases is controlled by a damper 32 located in the uptake 3| and provided with an operating arm 33. In order to control the air flow through the fan 19 a damper 35 is associated therewith, and in the embodiment illustrated this damper is located at the outlet of the fan, between the fan and the air chamber I8. The damper 35 is provided with an operating arm 36.

The electric motor 20 is started and stopped at intervals in accordance with the demand for heat. For this purpose the motor is connected to a suitable electrical supply 38 by means of conductors 39 which lead through an electromagnetically actuated switch or contactor 40. This switch is provided with a holding coil 42, and the parts are so arranged that upon energization of this coil the switch will be closed and the motor 20 will start. The current supply to the coil 42 is controlled by a pressure-actuated master switch 43 of the well-known mercury tube type connected by a pipe 44 to the steam delivery pipe 46 of the boiler 30 and arranged to close at a predetermined minimum steam pressure and to open at a predetermined maximum steam pressure. This switch 43 serves to control the supply of electricity from a suitable source 41 to a pair of wires 48 which connect with the coil 42.

Means is provided to close the dampers 32 and 35 when the stoker is shut down and to open these dampers when the stoker is started. In this manner excessive air flow through the furnace during the shut down periods can be prevented. For this purpose I provide a hydraulic motor 50 comprising a. cylinder 5|, a piston 52 slidable therein, and a piston rod 53 which is connected to the damper operating arm 33. A coiled compression spring 55 urges the piston 52 in a direction to close the damper 32, and adjustable set screws 56 limit the movement of the arm 33 in opposite directions. The motor 53 is actuated by the pressure of liquid supplied by the pump 22, this pressure being transmitted from the pump delivery pipe 21 to the cylinder 51 through a pipe 51. The damper is actuated by a similar hydraulic motor comprising a cylinder 6|, a piston 62 slidable therein, and a piston rod 63 which is connected to the damper operating arm 36. A coiled compression spring 65 urges the piston 62 in a direction to close the damper 35, and adjustable set screws 66 limit the movement of the arm 36 in opposite directions. A pipe 6! leads from/ the pump delivery pipe 21 to the cylinder 6|.

It will now be apparent that with the construction as so far described the springs and 55 will maintainthe dampers 32 and 35 substantially closed so long as the stoker is shut down,

but when the motor 20 starts and the pump 22 is actuated liquid will be supplied under pressure through the pipe 21 to the hydraulic motor I6, driving the stocker [2. Liquid will also flow through the pipes 51 and 61 to the motors 55 and respectively, opening the furnace dampers. If the forced draft damper 35 is opened too quickly, however, an excessive pressure may be created in the combustion chamber H, and the same thing may occur if the uptake damper 32 is closed too quickly when the stoker is shut down. In order to avoid this difliculty I preferably provide means to retard the opening movement of the forced draft damper and to retard the closing movement of the uptake damper.

For this purpose I mount a check valve 15 in the pipe 51, this check valve having a valve member H of the swing type arranged toopen freely in the direction of flow toward the motor 50, and I provide a small port or opening 12 through this valve member, as shown in Fig. 2. I also mount a check valve 15 in the pipe 51 with a valve member 16 therein of the swing type arranged to open freely in the direction of flow away from the motor 50, this valve member having a small port or opening 11 therethrough, as shown in Fig. 3. These ports 12 and 11 form restricted by-passes for their respective valve members.

The operation of the invention will now be apparent from the above disclosure. So long as the steam pressure in the boiler 30 is above a predetermined value the master switch 43 will be open, the stoker I2 will be shut down, and the dampers 32 and 35 will be held substantially closed by the springs 55 and 55. As the steam is used the pressure will'eventually drop suificiently to close the switch 43, energizing the coil 42 and closing the switch 40, thus starting the motor 20, the fan l9, and the pump 22. The pump will deliver oil under pressure through. the pipe 21 to the hydraulic motor l6 which will operate the stoker l2, and this pressure will be transmitted through the pipe 51 to the motor 55, quickly opening the uptake damper 32. Oil will also flow under pressure through the pipe 61 to the motor 68 to open the forced draft damper 35, but since this oil will have to pass through the small port 11 in the check valve 15 the opening movement of this damper will take place slowly, and there will be no appreciable increase in the pressure in the combustion chamber. When the steam pressure has increased sufficiently to open the master switch 43 the coil 42 will be de-energized, the switch 5!! will open, and the electric motor 25 will stop, stopping the fan l9 and the pump 22.

The pressure in the pipe 21 will immediately drop, and the spring will quickly close the forced draft damper 35. At the same time the spring 55 will start to close the uptake damper 32, but this closing movement will take place slowly since the oil which leaves the cylinder 5| must pass through the small port 12 in the check valve 13. Consequently any detrimental increase in the combustion chamber pressure will be avoided.

The apparatus disclosed is simple and inexpensive to manufacture and thoroughly reliable in operation.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A regulating system for a furnace having a forced draft fan to supply air to the furnace for combustion and an uptake damper to control the discharge of gases from the furnace comprising a pump arranged to supply liquid under pressure, means to start and stop the fan and pump in accordance with the demand for heat from the furnace, a hydraulic motor connected to the damper, a conduit connecting the pump with the motor, the motor being actuated by liquid delivered by the pump and arranged to open the damper when the pump is started, means to close the damper when the pump is stopped, a check valve in the conduit having a valve member arranged to open freely when the flow of liquid is toward the motor, and a restricted by-pass for the valve member. 7

2. A regulating system for a furnace having a forced draft fan to supply air to the furnace for combustion and an uptake damper to control the discharge of gases from the furnac comprising a pump arranged to supply liquid under pressure, means to start and stop the fan and pump in accordance with the demand for heat from the furnace, a hydraulic motor connected to the damper to open the same, a pipe connecting the pump with th motor, means to close the damper when the pump is stopped, and a check valve in the pipe having a valve member arranged to open freely in the direction of flow toward the motor, the valve member having a small opening therethrough for the flow of liquid during the closing movement of the damper.

3. A regulating system for a furnace having a forced draft fan to supply air to the furnace for combustion and a forced draft damper associated with the fan to control the air supply comprising a pump arranged to supply liquid under pressure, means to start and stop the fan and pump in accordance with the demand for heat from the furnace, a hydraulic motor connected to the damper to open the same, a pipe. connecting the pump with the motor, means to close the damper when the pump is stopped, and a check valve in the pipe having a valve member arranged to open freely when the flow of liquid is away from the motor, the valve member having a small opening therethrough for the flow of liquid in the other direction.

4. A regulating system for a furnace having a forced draft fan to supply air to the furnace for combustion, a forced draft damper associated with the fan to control the air supply, and an uptake damper to control the discharge of gases from the furnace comprising a pump arranged to supply liquid under pressure, means to start and stop the fan and pump in accordance with the demand for heat from the furnace, a separate motor being arranged to open freely when the flow of liquid is away from said motor, and the valve member associated with the uptake damper motor being arranged to open freely when the 5 flow of liquid is toward said motor.

RALPH C. MEAD. 

